Horrible PostgreSQL performance with NFS

[David Miller]

Arne Woerner wrote:

>--- Slawek Zak <slawek.zak at gmail.com> wrote:
>  
>
>>On 1/13/06, Arne Woerner <arne_woerner at yahoo.com> wrote:
>>40MB/s. CPU load negligible. I don't have
>>an exact number, as this machine has other
>>processes running. But overall, the system
>>load didn't exceed 5%.
>>
>>    
>>
>Looks good...
>
>  
>
>>I saturated fast ethernet on the host
>>with this test. Filer is connected with
>>Gb and can spew around 70MB/s easily.
>>CPU load on the host didn't exceed 4%.
>>
>>    
>>
>Looks even better... :-)
>
>  
>
>>>3. test the NIC performance with
>>>      
>>>
>>Filer doesn't respond to large icmp packets.
>>
>>    
>>
>Ok... This isn't so important, since NFS speed is higher than
>local disc speed.
>
>  
>
>>>My theory would be, that your NICs need a
>>>lot of CPU time, while your local discs
>>>dont need so much CPU time. :-)
>>>      
>>>
>>I don't think so. Drivers account for system
>>time. It doesn't exceed 20% of overall load.
>>The postgres processes are very busy doing
>>almost nothing. Semops is most of the work
>>they seem to do.
>>
>>    
>>
>Hmm...
>
>But why does switching from local disc to NFS makes the PostgreSQL
>performance so bad?
>  
>

It certainly sounds like something is no longer caching things - either 
reads or writes or both - when using NFS.

Does FreeBSD 6.x have a version of lockd that works with the netApp?



--- David